The application relates to the field of mobile wheeled equipment and specifically to camera dollies and cranes used in the television and motion picture industries. In the production of television programs or motion pictures, it is often necessary to maneuver a camera between different filming positions. The required camera movement may include elevating and lowering the camera as well lateral and longitudinal movement between the camera and subject. Continuous translation of the camera, i.e., to follow an action or moving sequence is also occasionally called for. Camera cranes and dollies are employed to support the camera and perform the desired camera movement.
For filming in close quarters, a compact camera dolly is desired. For example, to fit through narrow doorways, the length and width of the camera dolly should be limited. With the advent of widespread "on location" filming, the camera dolly may have to be hand carried, e.g., up narrow stairways, across uneven outdoor terrain, etc. Accordingly, it is desirable for the camera dolly to be lightweight and easily carried.
It is important for the camera dolly to provide a stable platform for the camera, both at rest and when moving, since any shock, vibrations, jarring or rocking imparted by the dolly will cause the recorded film or video image sequence to "jump" unacceptably. Consequently, the dolly structure must be rigid and secure. The camera dolly should preferably also be capable of readily supporting not only a camera of substantial weight, but also a camera operator and a second individual such as a cinematographer, director, lighting specialist, etc. Preferably, the camera dolly is able to quickly, but silently and smoothly translate, rotate and elevate the camera. Quiet operation of all aspects of dolly movement, such as rolling, steering, turning and elevating or lowering a camera is especially important during the production of live television wherein even intermittent low or muffled equipment noise can be disruptive.
For added versatility, the camera dolly should be capable of both conventional steering and crab steering.
In conventional steering, typically the front wheels remain fixed and the rear wheels steer. In crab steering, all of the dolly wheels are steered together, thereby permitting the dolly to be moved in any direction. In certain filming sequences, it is necessary to shift between conventional and crab steering modes. This shifting must be performed quickly and smoothly. In addition, the camera dolly operators or dolly grips must continue to smoothly push the dolly while steering mode shifting is made, during a filming sequence. This can be difficult because shifting has heretofore required a free arm or leg to actuate a shift handle or lever and because shifting can only occur when the wheels are properly aligned.
In conventional steering, to maintain acceptable steering performance while the dolly is steered on a curved path, a conventional steering corrector or transmission is required. See, for example, U.S. Pat. No. 4,003,584 to Zelli. The corrector adjusts the steering angle of the camera dolly wheels to allow the camera dolly to properly track a curved path. This prevents any scraping or scrubbing of the wheels against the floor or supporting surface which would tend to vibrate and disturb the camera and filming sequence as well as increasing rolling friction or resistance.
For translational filming sequences over uneven surfaces, for example on outdoor terrain, track rails can be laid to provide smooth rolling surface for the camera dolly. The camera dolly should accordingly be able to quickly and easily be set up for use on track rails.
Both 3-wheel and 4-wheel camera dollies or 3-corner pedestals have been proposed and used in the past (generally having dual wheels at each corner). Three-wheel configurations are advantageous as they are stable, i.e., a tripod configuration, even on uneven ground. However, three-wheel dollies or pedestals are not well suited for operation on track or allowing for passage through narrow doorways without incurring unexceptable levels of "tilt line" stability. Four-wheel camera dollies can perform well on track and have much larger wheelbase ranges but can be less stable than three-wheel units. For example, a slight bump under a wheel of a four-wheel unit can cause it to rock or tip slightly (due to one corner of the vehicle losing contact with the ground). This results in poor "tilt line" performance, whereas a three-wheel unit would be largely unaffected because all corners maintain ground contact. Consequently, heretofore, there have been tradeoffs to be weighed in selecting a three-wheel or a four-wheel design.
Accordingly, it is an object of the invention to provide a camera dolly having improved conventional steering performance.
It is a further object of the invention to provide such a camera dolly which is exceptionally quiet in operation.
It is yet another object of the invention to provide such a camera dolly which can be readily shifted between conventional steering and crab steering.
It is yet another object of the invention to provide such a dolly which is relatively lightweight and portable yet which provides a stable and secure camera platform.
It is still another object of the invention to provide a four wheel camera dolly having advantages of both a three-wheel configuration and a four-wheel configuration.
It is still another object of the invention to provide a combination camera dolly/pedestal having a separable pedestal which can be removed and used apart from the dolly.
It is yet another object of the invention to provide an electronic steering mode shifter for automatically shifting between conventional steering and crab steering in a camera dolly.
It is yet a further object of the invention to provide such a steering mode shifter which can be preset to eliminate the need for manually actuating a steering mode shift handle or lever.
It is a further object of the invention to provide such a shifter which shifts smoothly, quietly and quickly.
Other and further objects and advantages will appear hereinafter.